A court-approved commitment to repair or replace six major O'ahu sewage pipes would still leave open the possibility that Honolulu will be fined for diverting 48 million gallons of raw sewage into the Ala Wai Canal last year, according to the U.S. Environmental Protection Agency.

A tentative agreement that the city, EPA, U.S. Justice Department and state Health Department plan to file in federal court soon would not immediately levy a fine for the sewage spill, however.

"The settlement that the parties are discussing does not resolve any penalty issues," EPA spokesman Dean Higuchi said. "All penalty matters will be deferred until later."

Officials have estimated that the work on the six "force mains," or major pressurized sewer pipes that send wastewater to treatment plants, would cost $300 million.

The city had already planned to spend that amount and do the work over several years, but an agreement in court would create an enforcement mechanism to ensure the projects are completed.

Some City Council members who were briefed privately by attorneys about the settlement proposal Wednesday understood that it also would preclude a fine for the Waikiki spill.

That may ultimately prove correct, but a fine would remain possible for a period of time that the city and EPA have not yet divulged publicly.

Council members were briefly shown copies of the proposed agreement but were not allowed to keep them, and other officials declined to discuss the deal while it is pending.

The council is scheduled to vote on the settlement May 2. It would then be filed in U.S. District Court in conjunction with a lawsuit the EPA has prepared.

The deal also will require redundant sewer lines in some areas to handle wastewater if a major pipe breaks.

Reach Johnny Brannon at jbrannon@honoluluadvertiser.com.